In general, cellular radio communication systems based on Orthogonal Frequency Division Multiplexing (OFDM) transmission, and with unitary or quasi-unitary frequency reuse factor, suffer from inter-cell interference. In particular, all 3GPP standards starting from Long Term Evolution (LTE, part of Release 8), and including LTE-Advanced (LTE-A, part of Release 10) and beyond, suffer in general from inter-cell interference, because they are based on OFDM for downlink (DL) transmission, and on Single-Carrier Frequency Division Multiple Access (SC-FDMA) for uplink (UL) transmission.
As is known, different methods for characterizing co-channel interference in radio communication systems have been presented in the past. In this connection, specific reference is made to Applicant's international patent applications WO 2008-095543 and WO 2008-096383.
Moreover, also different methods for coordinating intra-system interference in radio communication systems have been presented in the past. In this connection, specific reference is made to Applicant's international patent applications WO 2011/051981 and WO 2011/051980.
In detail, said Applicant's international patent applications teach how to characterize inter-cell interference and how to implement Inter-Cell Interference Coordination (ICIC) so as to mitigate interference between neighbouring cells. Additionally, said Applicant's international patent applications teach to exploit communications on X2 interface between e-Node Bs in order to coordinate scheduling in neighbouring cells taking into account inter-cell interference. The timing that characterizes the evolution of the coordination process can be relatively slow (e.g. one coordination cycle every several tens to hundreds of ms). Interference characterization can be achieved with the same measurements that User Equipments (UEs) already perform to assist handover and other common procedures for cellular networks.
Furthermore, as is known, an inter-operator spectrum sharing scenario exists when a plurality of operators, each owning and controlling a respective proprietary frequency spectrum, partially share their respective proprietary frequency spectrum.
In this connection, United States Patent Application US 2009/0191889 A1 discloses a method of controlling spectrum use in a first wireless communication system which is operable to take part in a spectrum assignment process involving a plurality of wireless communication systems including the first wireless communication system, in which spectrum assignment process one of the said wireless communication systems assigns a portion of spectrum to at least one of the other said wireless communication systems.
In particular, the method according to US 2009/0191889 A1 comprises effecting an instance of the spectrum assignment process in response to a trigger which is based on network conditions.
In detail, the method according to US 2009/0191889 A1 comprises calculating a traffic delivery success ratio for the first wireless communication system and effecting the instance of spectrum assignment process in response to the traffic delivery success ratio being under a predetermined threshold.
Specifically, according to US 2009/0191889 A1, calculating a traffic delivery success ratio comprises determining a ratio of the quantity of traffic delivered to/from the first wireless communication system to the quantity of traffic which was intended for delivery to/from the first wireless communication system.